Photographic color developer

ABSTRACT

A PHOTOGRAPHIC COLOR DEVELOPER MIXTURE, WHICH CONTAINS A COLOR DEVELOPER OF THE P-PHENYLENE DIAMINE SERIES AND A WATER SOFTENER OF THE AMINOPOLYCARBOXYLIC ACID SERIES AND IN ADDITION A WATER-SOLUBLE AROMATIC POLYHYDROXY COMPOUND HAVING AT LEAST TWO HYDROXYL GROUPS IN ORTHOPOSITION TO EACH OTHER, HAS IMPROVED STABILITY TO ATMOSPHERIC OXYGEN AND DOES NOT DEPOSIT CHALKY PRECIPITATES.

United States Patent U.S. Cl. 96-66.4 4 Claims ABSTRACT OF THE DISCLOSURE A photographic color developer mixture, which contains a color developer of the p-phenylene diamine series and a water softener of the aminopolycarboxylic acid series and in addition a water-soluble aromatic polyhydroxy compound having at least two hydroxyl groups in orthoposition to each other, has improved stability to atmospheric oxygen and does not deposit chalky precipitates.

The invention relates to an aqueous alkaline developer mixture for the production of coloured photographic images and with improved resistance to oxidation.

It is known that in addition to the developer substances which bring about photographic development of the exposed silver halide emulsion layers, other compounds may be added to photographic developers to improve other properties of the developer mixture, e.g. its resistance to oxidation or its stability against the precipitation of calcium compounds.

These compounds are known as sequestering agent types of water softeners. They serve primarily to prevent the formation of precipitates when using water which contains calcium for the preparation of the developer mixture.

The water softeners mainly used are polyphosphates, e.g. sodium hexametaphosphate, or carboxylic acids which contain amino groups, e.g. ethylene diaminotetracetic acid. The effectiveness of these compounds depends to a large extent on the composition of the developer. In black-andwhite developers, for example, water softeners from either of the two classes of compounds mentioned above may be used. Considerable difiiculties, on the other hand, arise in the case of colour photographic developers. Sodium hexametaphosphate, for example, is no longer satisfactory for modern high speed development processes which are carried out at elevated temperatures, and precipitates which contain calcium are formed within a fairly short time. Although ethylene diaminotetracetic acid is an excellent sequestering agent even for colour photographic developers, its usefulness is limited by the fact that it considerably reduces the stability of colour photographic developers. This effect is presumably due to accelerated decomposition of the substances which are added to improve the resistance to oxidation, e.g. hydroxylamine.

It is the object of the present invention to provide colour photographic developers which are stable to atmospheric oxygen and against the formation of chalky precipitates. It is a particular object of the invention to improve the stability of colour photographic developers which contain ethylene dit.-ninotetracetic acid.

An aqueous alkaline developer mixture for the production of colour photographic images which contains a colour developer of the p-phenylene diamine series and a water softener of the aminopolycarboxylic acid series and in particular ethylene diaminotetracetic acid has now been found which contains in addition a water-soluble aromatic polyhydroxyl compound which has two hydroxyl groups in other-position to each other.

It has been found especially suitable to use o-dihydroxy compounds of the benzene or naphthalene series, e.g. pyrocatechol, pyrocatechol-3,S-disulphonic acid, pyrogallol, gallic acid or 2,3-dihydroxy naphthalene-6-sulphonic acid.

Sulpho-substituted or carboxyl-substituted compounds are especially suitable because they have the required solubility in water. In addition to being soluble in water, the compounds to be used according to the invention must, of course, be photographically inert at the concentrations at which they are used and, in particular, they must not interfere with chromogenic development.

The concentration of the dihydroxy compounds in the colour developers according to the invention may vary within wide limits. It depends on the nature of the developer, the required effect and on the properties of the dihydroxy compounds. Concentrations of from 1 to 400 mg. per litre and preferably of from 1 to 200 mg. per litre have generally been found to give the best results. This depends largely on the molecular weight of the dihydroxy compound used.

The colour developers according to the invention may also contain the usual additives.

The following are examples of suitable colour developer substances of the p-phenylene diamine series: N,N-diethyl-p-phenylene diamine, N-ethyl-N-fl-hydroxyethyl-p-phenylene diamine, N-butyl-N-w-sulphobutyl-p-phenylene diamine, N-ethyl-N-methylsulphonylaminoethyl-p-phenylene diamine and 4-amino-3-methyldiethyl aniline.

The alkalis used may be sodium or potassium carbonate, sodium borate, sodium phosphate or sodium or potassium hydroxide.

The mixtures contain the usual antioxidants, e.g. hydroxylamine salts or alkali metal sulphites.

EXAMPLE 1 A developer which has the following composition is tested:

G. Potassium carbonate Sodium sulphite 4 Hydroxylamine sulphate 4 Potassium bromide 1 N,N-diethyl-p-phenylene diamine-sulphate 6 Water softener 4 Made up within water to 1000 ml.

The following substances are added as water softeners:

Developer 1 4 g. of sodium hexametaphosphate.

Developer 2 4 g. of the sodium salt of ethylene diaminotetracetic acid.

Developer 3 fl g. of the sodium salt of ethylene diaminotetracetic acid and 0.025 g. of pyrocatecho1-3,5-sulphonic acid.

The three developers were all aerated under the same conditions for 48 hours in a vessel and the quantity of developer substance, hydroxylamine and Na SO then still left was determined. The results of the analyses are shown in the following table.

The lack of stability of developer 2 as regards the developer substance is clear from the above table. Whereas in developer 3 according to the invention the concentration of developer substance is unchanged and in developer 1 it is only slightly changed, the quantity of developer substance has dropped almost to half in developer 2.

A similar result is obtained in the photographic test. Developers 1 and 3 provide colour wedges with the same step number and same density in the fresh state and after 48 hours aeration, whereas in the case of developer 2 the images obtained after 48 hours aeration have a much flatter gradation than those obtained with the fresh developer.

The quality of developer 1 is photographically satisfactory but if this developer is used in a developer apparatus which is operated at an elevated temperature, the developer becomes cloudy due to precipitated calcium compounds after only a few days and solid deposits are formed at the bottom of the development vessel and in the pipes.

EXAMPLE 2 A photographic colour developer of the following composition is tested as described in Example 1:

G. Water softener 4 Sodium sulphite 24 Potassium bromide 1 Potassium carbonate 100 Hydroxylamine sulphate 4 N-butyl-N-w-sulphobutyl-p-phenylene diamine 6.2

Made up with water to 1000 ml.

The following substances are added as water softeners:

Developer 4 4 g. of sodium hexametaphosphate.

Developer 5 4 g. of the sodium salt of ethylene diaminotetracetic acid.

Developer 6 The same as in developer 5 plus 0.025 g. of pyrocatechol-3,5-disulphonic acid.

The developers are analyzed in the fresh state and after a vigorous stream of air has been passed through for 48 hours as described in Example 1. The results of the analysis are shown in Table 2 below.

In addition, the above colour developers are tested by a photographic test. A commercial multilayered colour photographic material was exposed behind a grey step wedge in a conventional sensitometer and samples of this exposed material were then developed in the various colour developers. They were then bleached and fixed in a known manner.

The gradation is determined from the resulting wedges. The results obtained agree with the analytical results. Whereas in the case of developers 4 and 6 no difierence can be detected between the freshly prepared developer mixtures and the aerated mixtures, the treated developer bath 5 brings about a strongly flattened gradation.

EXAMPLE 3 A colour developer mixture is prepared in water having 15 German degrees of hardness and an iron content of 0.3 mg./l., using a colour developer substance, the sodium salt of ethylene diaminotetracetic acid as water softener and various aromatic o-dihydroxy compounds to increase the stability of the developer.

Various tests are carried out on the developer and the hydroxylamine content is then determined as a measure of its stability.

Ethylene diaminotetracetic acid in the form of the tetrasodium salt 1.2 Hydroxylamine sulphate 4 Sodium sulphite sicc 4 Potassium carbonate Potassium bromide 1 N-butyLN-w-sulphobutyl-p-phenylene diamine 6 Made up with water to, 1000 ml.

Developer 7 Without further additives. Developer 8 Pyrogallol, 0.025 g./l. Developer 9 Gallic acid, 0.03 g./l. Developer 10 Pyrrocatechol disnlphonic acid, 0.025 g/l. Developer 11 Potassium salt of 2,3-dihydroxy-naphthalene sulphonie acid-(6), 0.03 g./l. Developer 12 2,3,8-trihydroxy-naplithalene sulphonic acid-(6) 0.03 g./l.

In the test series A, the samples of developer were kept free from air for 10 days at 30 C. in bottles which were filled to the top.

In the test series B, the developers were kept in open vessels at room temperature for 10 days.

The samples of the test series C were kept at room temperature for 30 days in partly filled bottles to prevent excessive evaporation.

The results of these test series are summarised in Table 3.

TABLE 3 Hydroxylamine content in the various developers, g./1.

Test series A B C Developer No.2

The protective effect of the o-dihydroxyaryl compounds on the stability of hydroxylamine and hence of the colour developer is obvious.

EXAMPLE 4 The protective ell'ect of the o-dihydroxyaryl compounds can be demonstrated not only in developers which contain ethylene diaminotetracetic acid but also in developers which contain other water softeners :based on amino acetic acid, as will be clear from the following series of tests.

Various water softeners are added in each case to 2 litres of developer and the developer is then in each case divided into two portions of 1 litre and 0.1 g. of pyrocatechol disulphonic acid is added to one of the two portions. The samples were stored for 20 days at 30 C. in completely filled bottles. The hydroxylamine content is then determined.

Composition of the developer:

Water softener, see below.

G. Hydroxylamine sulphate 4 Sodium sulphite 4 Potassium carbonate 100 Potassium bromide 1 N-butyl-N-w-sulphobutyl-p-phenylene diamine 6 Developer 13 1.2 g. of ethylene diaminotetracetic acid in the form of the tetrasodium salt.

Developer 14 The same as developer 13 with the addition of 0.1 g. of pyroeatechol disulphonic acid.

Developer 15 4 g. of diethylene triaminopentacetic acid.

Developer 16 The same as developer 15 with the addition of 0.1 g. of pyrocatechol disulphonic acid.

Developer 17 4 g. of hydroxyethylethylene diaminotriacetic acid (41% in water).

Developer 18 The same as developer 17 with the addition of 0.1 g. of pyrocatechol disulphonic acid.

The results of the hydroxylamine determinations after 20 days storage in the laboratory at 30 c. are summarised in Table 4.

TABLE 4 Hydroxylamine contents of the developers, g./l.

Without With pyrocatpyrocatech ech disulphondisulphonic acid it: acid EXAMPLE Developer 19 Without further additives.

Developer 20 Tetrabromopyrocatechol, 0.032 g./l.

Developer 21 Tetrabromopyrocatechol, 0.320 g./l.

TABLE 5 Hydroxylamine content in g./l. after- 1 day 2 days 3 days 4 days 7 days Developer N 0.:

I claim:

1. An aqueous color developer composition containing a p-phenylene diamine color developer and an aminopolycarboxylic acid water softener, said composition also having a water soluble aromatic polyhydroxyl compound having at least two hydroxy groups in ortho-position in relation to each other on the aromatic ring, said aromatic polyhydroxyl compound being an o-dihydroxy compound of the benzene or naphalene series so as to stabilize the developer mixture to atmospheric oxygen and in an amount of from 1 to 400 mg. per liter.

2. A color developer composition according to claim 1 in which the o-dihydroxy compound is selected from the group consisting of pyrocatechol, pyrocatechol-3,5-disulphonic acid, pyrogallol, gallic acid and 2,3-dihydroxy naphthalene-6-sulphonic acid.

3. A color developer composition according to claim 1 in which the o-dihy lroxy compound is present in a concentration that provides between 1 and 200 mg. per liter of developer solution.

4. A color developer composition according to claim 1 in which the polyhydroxyl compound contains at least one sulfo or carboxyl group.

References Cited UNITED STATES PATENTS 2,875,049 2/ 1959 Kridel 96-664 3,134,673 5/1964 Gauguin 9655 3,201,246 8/1965 Allen 9695 3,265,502 8/1966 Willerns et al 96-66.5 3,462,269 8/1969 Tassone 96--55 3,520,690 7/1970 Nagae 9655 FOREIGN PATENTS 580,237 8/ 1946 Great Britain 96-66 R OTHER REFERENCES PSA Technical Quart, November 51954, vol. I, No. 4, pp. 126 and 127.

Journal of Photographic Science, vol. II, 1963, pp. 136-139, by Mason.

DAVID KLEIN, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. X.R. 96--55, 56, 66, 66.3 

